Crystal structure, magnetic and transport properties of new ruthenate phase, Ba2Ru7O18

A new phase of ternary ruthenium oxide, Ba2Ru7O18, is discovered. The lattice parameters are: trichnic, a = 6.71(4) Angstrom, b = 7.10(4) Angstrom, c = 7.46(4) Angstrom, alpha = 93.2(2)degrees, beta = 94.6(2)degrees, gamma = 115.7(2)degrees. It has a Ba2Zn7F18-type structure composed of an egde-shared and corner-shared network of RuO6 octahedra. The magnetic susceptibility around room temperature exhibits a Pauli paramagnetism with a relatively large value of X = 3.4 x 10(-4) emu/mol at 300 K, while it exhibits a large temperature dependence in the low temperature range without any evidence of magnetic phase transitions down to 2 K. The resistivity at 300 K is 1.1 X 10(-3) Q CM, larger than that of normal metal. Unlike conventional metals, the resistivity exhibits T-1.2-linear dependence in the low temperature region. These anomalous behaviors of magnetism and resistivity can be interpreted in terms of the non-Fermi liquid state.